Mike James
The Independent
OLIVE HILL —
Cave experts spent much of the week welding and fitting a strong steel gate across the back entrance of Bat Cave in the Carter Caves State Resort Park.
The gate replaces one that gave way and collapsed during heavy flooding earlier in the summer.
Its purpose is to keep people out of the cave, which is the winter home for thousands of Indiana bats.
In fact, Bat Cave is one of the most important caves in the United States for bat hibernation, said biologist Jim Kennedy, a cave and mine resource specialist for Bat Conservation International. More than 30,000 bats hibernate there every year.
Hibernation season starts in September and lasts until spring.
When bats hibernate, their metabolisms slow down dramatically and they use stored fat to live through the winter. If disturbed, their heart rate and respiration rise and they are likely to fly out of the cave, where they die for lack of food. Even if they remain in the cave they use too much of their stored energy and die before spring.
Roy Powers, a retired professor of electronic engineering, designed the gate, which is made of angle iron about six inches on each side. His design had to take into account flying space for the bats to get into the cave and also air flow. The angle iron bars have additional strips of steel welded inside to permit the air to slip smoothly past. It’s a design that has evolved over three decades, Powers said.
In fact, the design was tested in a wind tunnel to make sure it wouldn’t retard the free flow of air, he said. Less air flowing through the cave would change humidity levels, affect the bats’ environment, and possibly retard rock formations.
The space between the bars is calculated so bats can fly freely through. “It’s the first cave anywhere in the U.S. to have a bat-friendly gate,” Kennedy said.
The cave entrance has been gated since the 1960s. Gates don’t last forever, because the cave serves as a drain for a mile-long valley. Runoff washes debris to the cave mouth and during periods of heavy rainfall the water backs up, resulting in enormous pressure against the gate, Kennedy said.
The old gate lasted 10 years and was still sturdy but the rocks it was anchored to broke away, Powers said.
MIKE JAMES can be reached at mjames@dailyindependent.com or (606) 326-2652.
